[8doubles]

I remember reading somewhere that ants actively encourage blackfly up the stems of Broad Beans so that they can enjoy the secreting sap.  I certainly have blackfly on my BB's as of yesterday, where there were only ants last week.

On the other hand ants do not make the blackfly or aphids but they often draw your attention to them !

[LotuSeed]

They make great pollinators too!